Low incidence of p53 mutations in European hepatocellular carcinomas with heterogeneous mutation as a rare event

Serum Response Factor (SRF) Drives the Transcriptional Upregulation of the MDM4 Oncogene in HCC

Different molecular mechanisms support the overexpression of the mouse double minute homolog 4 (MDM4), a functional p53 inhibitor, in human hepatocellular carcinoma (HCC). However, the transcription factors (TFs) leading to its transcriptional upregulation remain unknown. Following promoter and gene expression analyses, putative TFs were investigated using gene-specific siRNAs, cDNAs, luciferase reporter assays, chromatin immunoprecipitation, and XI-011 drug treatment in vitro. Additionally, MDM4 expression was investigated in SRF-VP16iHep transgenic mice. We observed a copy-number-independent upregulation of MDM4 in human HCCs. Serum response factor (SRF), ELK1 and ELK4 were identified as TFs activating MDM4 transcription. While SRF was constitutively detected in TF complexes at the MDM4 promoter, presence of ELK1 and ELK4 was cell-type dependent. Furthermore, MDM4 was upregulated in SRF-VP16-driven murine liver tumors. The pharmacological inhibitor XI-011 exhibited anti-MDM4 activity by downregulating the TFs driving MDM4 transcription, which decreased HCC cell viability and increased apoptosis. In conclusion, SRF drives transcriptional MDM4 upregulation in HCC, acting in concert with either ELK1 or ELK4. The transcriptional regulation of MDM4 may be a promising target for precision oncology of human HCC, as XI-011 treatment exerts anti-MDM4 activity independent from the MDM4 copy number and the p53 status.

Immunohistochemical Determination of p53 Protein Overexpression for Predicting p53 Gene Mutations in Hepatocellular Carcinoma: A Meta-Analysis

BACKGROUND

Whether increased expression of the tumor suppressor protein p53 indicates a p53 gene mutation in hepatocellular carcinoma (HCC) remains unclear. We conducted a meta-analysis to determine whether p53 protein overexpression detected by immunohistochemistry (IHC) offers a diagnostic prediction for p53 gene mutations in HCC patients.

METHODS

Systematic literature searches were conducted with an end date of December 2015. A meta-analysis was performed to estimate the diagnostic accuracy of IHC-determined p53 protein overexpression in the prediction of p53 gene mutations in HCC. Sensitivity, subgroup, and publication bias analyses were also conducted.

RESULTS

Thirty-six studies were included in the meta-analysis. The results showed that the overall sensitivity and specificity for IHC-determined p53 overexpression in the diagnostic prediction of p53 mutations in HCC were 0.83 (95% CI: 0.80-0.86) and 0.74 (95% CI: 0.71-0.76), respectively. The summary positive likelihood ratio (PLR) and negative likelihood ratio (NLR) were 2.65 (95% CI: 2.21-3.18) and 0.36 (95% CI: 0.26-0.50), respectively. The diagnostic odds ratio (DOR) of IHC-determined p53 overexpression in predicting p53 mutations ranged from 0.56 to 105.00 (pooled, 9.77; 95% CI: 6.35-15.02), with significant heterogeneity between the included studies (I2 = 40.7%, P = 0.0067). Moreover, subgroup and sensitivity analyses did not alter the results of the meta-analysis. However, potential publication bias was present in the current meta-analysis.

CONCLUSION

The upregulation of the tumor suppressor protein p53 was indeed linked to p53 gene mutations. IHC determination of p53 overexpression can predict p53 gene mutations in HCC patients.

[EEF1A2 inhibits the p53 function in hepatocellular carcinoma via PI3K/AKT/mTOR-dependent stabilization of MDM4]

Upregulation of mouse double minute 4 (MDM4) is a frequent event in human hepatocellular carcinoma (HCC) but the underlying molecular mechanisms are poorly characterized. In this study a potential role of the phosphoinositide-3-kinase/v-AKT murine thymoma viral oncogene homolog/mammalian target of rapamycin (PI3K/AKT/mTOR) cascade was investigated in the regulation of MDM4 in HCC. Inhibition of the PI3K-AKT and/or mTOR pathways lowered MDM4 protein levels in HCC cells. Mechanistic protection from proteasomal degradation resulted from de-ubiquitination by ubiquitin-specific protease 2a and AKT-mediated phosphorylation of MDM4, thus increasing MDM4 protein levels. These findings were corroborated in a chimeric AKT mouse model. Upregulation of PI3K/AKT/mTOR signaling may result from overexpression of the eukaryotic elongation factor 1A2 (EEF1A2). Finally, a strong association between the expression of EEF1A2, phosphorylated AKT and MDM4 was observed in human HCC samples. Strong activation of the EEF1A2/PI3K/AKT/mTOR/MDM4 signaling pathway was observed in HCC patients with short survival suggesting that targeting this axis might be a promising approach in a subset of HCC patients.

Prosurvival function of the cellular apoptosis susceptibility/importin-α1 transport cycle is repressed by p53 in liver cancer

Proteins of the karyopherin superfamily including importins and exportins represent an essential part of the nucleocytoplasmic transport machinery. However, the functional relevance and regulation of karyopherins in hepatocellular carcinoma (HCC) is poorly understood. Here we identified cellular apoptosis susceptibility (CAS, exportin-2) and its transport substrate importin-α1 (imp-α1) among significantly up-regulated transport factor genes in HCC. Disruption of the CAS/imp-α1 transport cycle by RNAi in HCC cell lines resulted in decreased tumor cell growth and increased apoptosis. The apoptotic phenotype upon CAS depletion could be recapitulated by direct knockdown of the X-linked inhibitor of apoptosis (XIAP) and partially reverted by XIAP overexpression. In addition, XIAP and CAS mRNA expression levels were correlated in HCC patient samples (r=0.463; P<0.01), supporting the in vivo relevance of our findings. Furthermore, quantitative mass spectrometry analyses of murine HCC samples (p53-/- versus p53+/+) indicated higher protein expression of CAS and imp-α1 in p53-/- tumors. Consistent with a role of p53 in regulating the CAS/imp-α1 transport cycle, we observed that both transport factors were repressed upon p53 induction in a p21-dependent manner.

CONCLUSION

The CAS/imp-α1 transport cycle is linked to XIAP and is required to maintain tumor cell survival in HCC. Moreover, CAS and imp-α1 are targets of p53-mediated repression, which represents a novel aspect of p53's ability to control tumor cell growth in hepatocarcinogenesis.

EEF1A2 inactivates p53 by way of PI3K/AKT/mTOR-dependent stabilization of MDM4 in hepatocellular carcinoma

Mouse Double Minute homolog 4 (MDM4) gene up-regulation often occurs in human hepatocellular carcinoma (HCC), but the molecular mechanisms responsible for its induction remain poorly understood. Here we investigated the role of the phosphoinositide-3-kinase/v-akt murine thymoma viral oncogene homolog/mammalian target of rapamycin (PI3K/AKT/mTOR) axis in the regulation of MDM4 levels in HCC. The activity of MDM4 and the PI3K/AKT/mTOR pathway was modulated in human HCC cell lines by way of silencing and overexpression experiments. Expression of main pathway components was analyzed in an AKT mouse model and human HCCs. MDM4 inhibition resulted in growth restraint of HCC cell lines both in vitro and in vivo. Inhibition of the PI3K-AKT and/or mTOR pathways lowered MDM4 protein levels in HCC cells and reactivated p53-dependent transcription. Deubiquitination by ubiquitin-specific protease 2a and AKT-mediated phosphorylation protected MDM4 from proteasomal degradation and increased its protein stability. The eukaryotic elongation factor 1A2 (EEF1A2) was identified as an upstream inducer of PI3K supporting MDM4 stabilization. Also, we detected MDM4 protein up-regulation in an AKT mouse model and a strong correlation between the expression of EEF1A2, activated/phosphorylated AKT, and MDM4 in human HCC (each rho > 0.8, P < 0.001). Noticeably, a strong activation of this cascade was associated with shorter patient survival.

CONCLUSION

The EEF1A2/PI3K/AKT/mTOR axis promotes the protumorigenic stabilization of the MDM4 protooncogene in human HCC by way of a posttranscriptional mechanism. The activation level of the EEF1A2/PI3K/AKT/mTOR/MDM4 axis significantly influences the survival probability of HCC patients in vivo and may thus represent a promising molecular target.

Strategies for hepatocellular carcinoma therapy and diagnostics: lessons learned from high throughput and profiling approaches

Over the last decade, numerous small and high-dimensional profiling analyses have been performed in human hepatocellular carcinoma (HCC), which address different levels of regulation and modulation. Because comprehensive analyses are lacking, the following review summarizes some of the general results and compares them with insights from other tumor entities. Particular attention is given to the impact of these results on future diagnostic and therapeutic approaches.

249 TP53 mutation has high prevalence and is correlated with larger and poorly differentiated HCC in Brazilian patients

Background

Ser-249 TP53 mutation (249^Ser) is a molecular evidence for aflatoxin-related carcinogenesis in Hepatocellular Carcinoma (HCC) and it is frequent in some African and Asian regions, but it is unusual in Western countries. HBV has been claimed to add a synergic effect on genesis of this particular mutation with aflatoxin. The aim of this study was to investigate the frequency of 249^Ser mutation in HCC from patients in Brazil.

Methods

We studied 74 HCC formalin fixed paraffin blocks samples of patients whom underwent surgical resection in Brazil. 249^Ser mutation was analyzed by RFLP and DNA sequencing. HBV DNA presence was determined by Real-Time PCR.

Results

249^Ser mutation was found in 21/74 (28%) samples while HBV DNA was detected in 13/74 (16%). 249^Ser mutation was detected in 21/74 samples by RFLP assay, of which 14 were confirmed by 249^Ser mutant-specific PCR, and 12 by nucleic acid sequencing. All HCC cases with p53-249ser mutation displayed also wild-type p53 sequences. Poorly differentiated HCC was more likely to have 249^Ser mutation (OR = 2.415, 95% CI = 1.001 – 5.824, p = 0.05). The mean size of 249^Ser HCC tumor was 9.4 cm versus 5.5 cm on wild type HCC (p = 0.012). HBV DNA detection was not related to 249^Ser mutation.

Conclusion

Our results indicate that 249^Ser mutation is a HCC important factor of carcinogenesis in Brazil and it is associated to large and poorly differentiated tumors.

Pifithrin-alpha enhances chemosensitivity by a p38 mitogen-activated protein kinase-dependent modulation of the eukaryotic initiation factor 4E in malignant cholangiocytes

Pifithrin-alpha is the lead compound for a novel group of small molecules that are being developed for use as anticancer agents. The eukaryotic initiation factor 4E (eIF-4E) is overexpressed in many cancers, it can mediate sensitivity to therapy, and it may be regulated by p53. We examined the utility of pifithrin-alpha as an adjunct to therapy for the treatment of human cholangiocarcinoma, a tumor that is highly refractory to therapy, and we assessed the involvement of p53-dependent eIF-4E regulation in cellular responses to pifithrin-alpha. The expression of eIF-4E was increased in human cholangiocarcinomas compared with normal liver. Modulation of eIF-4E expression by RNA interference enhanced the efficacy of gemcitabine in KMCH cholangiocarcinoma cells. Preincubation of KMCH cells with pifithrin-alpha enhanced gemcitabine-induced cytotoxicity in an eIF-4E-dependent manner. Furthermore, pifithrin-alpha increased eIF-4E phosphorylation at serine 209 via activation of p38 mitogen-activated protein kinase (MAPK). Pifithrin-alpha was shown to activate aryl hydrocarbon receptor (AhR) signaling and p38 MAPK activation. Sequencing analysis indicated the presence of a functionally inactivating p53 mutation in KMCH cells, and small interfering RNA to p53 did not modulate chemosensitization by pifithrin-alpha. Pifithrin-alpha enhanced chemosensitivity by a mechanism independent of p53 and involving AhR and p38 MAPK deregulation of eIF-4E phosphorylation. Thus, pifithrin-alpha may prove useful for enhancing chemosensitivity in tumors with mutated p53. Moreover, modulation of eIF-4E is an attractive therapeutic target for intervention in cancer treatment.

Genetic alterations in cancer knowledge system: analysis of gene mutations in mouse and human liver and lung tumors

Mutational incidence and spectra for genes examined in both human and mouse lung and liver tumors were analyzed using the National Institute of Environmental Health Sciences (NIEHS) Genetic Alterations in Cancer (GAC) knowledge system. GAC is a publicly available, web-based system for evaluating data obtained from peer-reviewed studies of genetic changes in tumors associated with exposure to chemical, physical, or biological agents, as well as spontaneous tumors. In mice, mutations in Kras2 and Hras-1 were the most common events reported for lung and liver tumors, respectively, whether chemically induced or spontaneous. There was a significant difference in Kras2 mutation incidence for spontaneous versus induced mouse lung tumors and in Hras-1 mutation incidence and spectrum for spontaneous versus induced mouse liver tumors. The major gene changes reported for human lung and liver tumors were in KRAS2 (lung only) and TP53. The KRAS2 mutation incidence was similar for spontaneous and asbestos-induced human lung tumors, while the TP53 mutation incidence differed significantly. Aflatoxin B1, hepatitis B virus, hepatitis C virus, and vinyl chloride all caused TP53 mutations in human liver tumors, but the mutation spectrum for each agent differed. The incidence of KRAS2 mutations in human compared to mouse lung tumors differed significantly, as did the incidence of Hras and p53 gene mutations in human compared to mouse liver tumors. Differences observed in the mutation spectra for agent-induced compared to spontaneous tumors and similarities in spectra for structurally similar agents support the concept that mutation spectra can serve as a "fingerprint" of exposure based on chemical structure.

Orthotopic implantation of human hepatocellular carcinoma in mice: analysis of tumor progression and establishment of the BCLC-9 cell line

PURPOSE

To allow the longitudinal investigation of molecular events associated with the progression of human hepatocellular carcinoma (HCC), we sought to develop a murine model by orthotopic implantation of tumor fragments obtained from patients diagnosed at early stage.

EXPERIMENTAL DESIGN

Tumor pieces (2 x 2 mm) were implanted on the liver surface of nu/nu mice. After xenograft growing, subsequent passages were performed to achieve long-term implant viability. Isolation of tumoral hepatocytes was done to establish new cell lines. HCC characteristics, proliferation rate, apoptotic index (terminal deoxynucleotidyl transferase-mediated nick end labeling), and expression of cell-cycle regulators (cyclins E and A, p21(Cip1), p27(Kip1), p16(INK4a), pRb, and p53) were assessed by Western Blot and immunohistochemistry, to correlate them with tumor progression.

RESULTS

Five (50%) of the 10 primary HCCs resulted in small slow-growing liver implants. Three of them are viable after 48 months, whereas the remaining two survived for 15 and 13 months. Xenografts throughout passages exhibited a more aggressive phenotype with a poorer degree of differentiation, intense proliferation, moderate apoptosis, cell-cycle deregulation, p53 alterations, microvascular invasion, and dissemination. In one single passage, we observed critical growth delay, which was associated with significant p27(kip1) overexpression. We established the anchor-free growing BCLC-9 cell line from one xenograft. This has gains of chromosomes 7, 5p, 6q, and 9q, is hepatitis B virus-DNA positive, does not secrete alpha-fetoprotein, and has TP53 missense mutations in codons 192 and 242.

CONCLUSIONS

The orthotopic implantation of early HCC fragments in nude mice provides a useful model to investigate the mechanisms of human HCC evolution and to establish new cell lines.

Detecção imunoistoquímica das oncoproteínas p21ras, c-myc E p53 no carcinoma hepatocelular e no tecido hepático não-neoplásico

RACIONAL: A hepatocarcinogênese é um processo no qual as alterações genéticas e epigenéticas são bem conhecidas em modelos animais, mas carece de estudos no homem. OBJETIVOS: Analisar a freqüência das oncoproteínas p21ras, c-myc e p53 no carcinoma hepatocelular e no fígado não-neoplásico. Verificar ainda a associação destas oncoproteínas com os padrões e graus histológicos, assim como com as infecções pelos vírus das hepatites B e C. MÉTODOS: Foi analisada por método imunoistoquímico a detecção das oncoproteínas p21ras, c-myc e p53 em 47 casos de carcinoma hepatocelular e no tecido não-neoplásico circunjacente ao tumor (40 casos). RESULTADOS: As oncoproteínas p21ras, c-myc e p53 foram detectadas, respectivamente, em 44,7%, 53,2% e 36,2% dos casos de carcinoma hepatocelular. A imunorreatividade do p21ras e c-myc mostrou uma associação significativa. Contudo, não houve associação significativa entre a detecção do p21ras, c-myc e p53 com os diferentes graus e padrões histológicos, nem tampouco com as infecções pelos vírus das hepatites B e C. A mesma associação significativa entre o p21ras e c-myc foi encontrada no tecido não-neoplásico dos casos de cirrose em relação aos que não apresentaram cirrose, enquanto que o p53 foi negativo em todos os casos. CONCLUSÕES: A imunorreatividade das oncoproteínas p21ras, c-myc e p53 corrobora evidências prévias de sua detecção no carcinoma hepatocelular, o que sugere poder haver participação destas proteínas na hepatocarcinogênese humana. A significativa associação entre as proteínas p21ras, c-myc e p53 no carcinoma hepatocelular e na cirrose pode apontar uma interação entre as mesmas, sobretudo na hepatocarcinogênese pela via da cirrose.

Hepatocyte growth factor, transforming growth factor alpha, and their receptors as combined markers of prognosis in hepatocellular carcinoma

A change in the balance between proliferation and apoptosis in the course of hepatocellular carcinoma (HCC) development and progression has been suspected. We wanted to identify related genes whose mRNA levels could provide markers of severity and prognosis after resection. The extent of cell apoptosis, proliferation, and differentiation was measured with a terminal deoxynucleotidyl transferase-mediated deoxyuridine 5-triphosphate-biotin nick-end labeling assay, and the Ki-67 index was determined in paired tumor and cirrhotic tissue samples from patients who had undergone HCC resection after diagnosis of hepatitis C-related or alcoholism-related cirrhosis. These patients included two groups with highly versus poorly differentiated tumor cells, and the latter was split into two subgroups of those with versus without early recurrence. The mRNA levels for various apoptosis-related or proliferation-related genes and those for the growth factor/receptor systems were measured by quantitative reverse transcriptase-polymerase chain reaction in paired tumor and cirrhotic liver samples from every patient, and some of the corresponding proteins were detected by immunohistochemistry. In all instances, protein expression was highly heterogeneous within groups and similar between groups. In contrast, some differences in mRNA level between tumor and cirrhotic tissues were quite informative. Low levels of hepatocyte growth factor and transforming growth factor alpha mRNAs were found concomitantly in highly differentiated tumors, whereas overexpression of mRNAs for the cognate receptors c-met and epidermal growth factor receptor were found in poorly differentiated tumors and primarily in patients with early tumor recurrence. These results argue for growth factor-dependent HCC development and provide novel and combined prognosis markers after HCC surgery.

Pathogenesis of hepatocellular carcinoma

The pathogenesis of HCC is poorly understood at present. There is insufficient understanding to propose a robust general model of hepatic carcinogenesis, partly because pathogenic host and environmental factors show significant regional variation, making such generalization difficult. Figure 4 is a model based on data presented in this article. Multiple risk factors for HCC have been identified, including cirrhosis, male gender, increasing patient age, toxins, chronic viral hepatitis, and other specific liver diseases. The understanding of how the individual risk factors result in genetic changes is rudimentary, and there is even less understanding about interactions between risk factors. Future studies should acknowledge the geographic origin of the HCCs studied and consider the effects of cirrhosis, gender, and age. A more rigorous approach to these factors may help explicate the interaction with specific liver diseases so that a comprehensive model of hepatic carcinogenesis can be developed.

Genetics of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the human cancers clearly linked to viral infections. Although the major viral and environmental risk factors for HCC development have been unravelled, the oncogenic pathways leading to malignant transformation of liver cells have long remained obscure. Recent outcomes have been provided by extensive allelotype studies which resulted in a comprehensive overview of the main genetic abnormalities in HCC, including DNA copy gains and losses. The differential involvement of the p53 tumor-suppressor gene in tumors associated with various risk factors has been largely clarified. Evidence for a crucial role of the reactivation of the Wnt/beta-catenin pathway, through mutations in the beta-catenin and axin genes in 30-40% of liver tumors, represents a major breakthrough. It has also been shown that the Rb pathway is frequently disrupted by methylation-dependent silencing of the p16INK4A gene and stimulation of Rb degradation by a proteosomal subunit. Presently, the identification of candidate oncogenes and tumor suppressors in the most frequently altered chromosomal regions is a major challenge. Great insights will come from integrating the signals from different pathways operating at preneoplastic and neoplastic stages. This search might, in time, permit an accurate evaluation of the major targets for therapeutic treatments.

p53 represses CAAT enhancer-binding protein (C/EBP)-dependent transcription of the albumin gene. A molecular mechanism involved in viral liver infection with implications for hepatocarcinogenesis

p53 is a transcription factor that is activated by genotoxic stress and mediates cell cycle arrest and apoptosis. Here we demonstrate that infection of mouse liver with recombinant E1/E3-deleted adenovirus leads to p53 activation and simultaneously to the down-regulation of albumin gene expression. In vitro transcription assays indicate that transcriptional mechanisms mediated through the albumin promoter are responsible for reduced albumin mRNA levels during viral infection. Albumin expression is maintained in the liver by a combination of liver-enriched transcription factors such as CAAT enhancer-binding protein (C/EBP)alpha and C/EBPbeta. We show that p53 wild type and tumor-derived p53 mutations repress C/EBP-mediated transactivation of the albumin promoter. The binding of C/EBPalpha or -beta to its cognate sequence in the albumin promoter is not inhibited by p53 expression. Deletion analysis and domain swapping experiments show that repression of C/EBPbeta-mediated transactivation is dependent on the N-terminal domain of p53 and the transactivation domain, leucine zipper domain, and the inhibitory domain II (amino acids 163-191) of C/EBPbeta. Our results provide a molecular explanation for the p53-mediated down-regulation of liver-specific gene expression after viral infection. Additionally, as overexpression of p53 mutants is frequently found in undifferentiated hepatocellular carcinomas, the same mechanisms may contribute to the lack of liver-specific gene transcription in these tumors.

Microsatellite instability and p53 mutations in hepatocellular carcinoma

We have studied 27 hepatocellular carcinomas (HCCs) to identify possible relationships between microsatellite instability (MSI), p53 mutations, and HBV infection in hepatocarcinogenesis. MSI was assessed using 19 polymorphic markers and the poly(A) tract BAT-26. All coding regions of p53 were examined for mutations. Tumors were also examined for presence of hepatitis B virus (HBV) DNA sequences; 66.6% of the samples exhibit MSI in at least one microsatellite locus and 44% in two or three loci. None of the tumors examined showed alterations in BAT-26. Moreover, 73.3% of samples with indication of HBV infection showed instability in at least one marker. No association between MSI and pathological profile was found. Five (18.5%) samples harbored mutations in p53, three missense, and two insertions, all in exons 5 and 8 not previously reported. No mutations were detected in codon 249, which has been linked with dietary intake of aflatoxins. Our results support the hypothesis that HCC is a "low" MSI tumor. Only 1/5 samples with MSI in more than two markers harbored a mutation in p53. Although the number of samples is too small to support a statistical significance, this finding may indicate an inverse relationship between p53 mutations and MSI in HCC.

Genetic alterations in hepatocellular carcinomas: association between loss of chromosome 4q and p53 gene mutations

The major risk factors for hepatocellular carcinomas (HCC) in high incidence areas include infection with hepatitis B and C viruses (HBV, HCV) and exposure to aflatoxin. Genetic alterations in 24 liver resection specimens from Shanghai and Qidong were studied. Hepatitis B virus was integrated in all patient samples, and a null phenotype for the GSTM1 enzyme was present in 63% of patients. Alteration of p53 was present in 95% (23/24) of cases: mutations of the p53 gene in 12 HCC, p53 overexpression in 13 and loss of heterozygosity (LOH) of chromosome 17p in 17. All seven HCCs with a p53 mutation from Qidong and three of five from Shanghai had the aflatoxin-associated point mutation with a G to T transversion at codon 249, position 3. No HCC had microsatellite instability. LOH of chromosome 4q, 1p, 16q and 13q was present in 50%, 46%, 42% and 38%, respectively, and 4q was preferentially lost in HCCs containing a p53 mutation: LOH of 4q was present in 75% (9/12) of HCC with, but only 25% (3/12) of HCC without, a p53 gene mutation (P = 0.01). These data indicate a possible interaction between p53 gene mutation and 4q loss in the pathogenesis of HCC.

Hepatitis B virus mutations in the pre-S genome before and after liver transplantation

Mutational changes in the pre-S region of hepatitis B virus (HBV) were analyzed in 20 patients who experienced HBV reinfection after orthotopic liver transplantation (OLT). HBV DNA was extracted from patient sera before and after OLT. The pre-S sequence was amplified via polymerase chain reaction, subcloned, sequenced, and analyzed. In 18 of 20 patients, mutational changes were found in the pre-S region pre- or post- OLT; 11 showed point mutations (1-10) and 7 cases major changes (insertions/deletions). For the point mutations, there was no trend in the selection of wild-type (wt) HBV before or after OLT in the pre-S region. Additional HBV reinfection during hepatitis B surface antigen antibody (anti-HBS) administration had no influence on selection pressure in the pre-S region. In contrast, insertions/deletions were more frequently found before OLT. In the 7 patients with deletions/insertions, changes in the hepatocyte attachment site were not seen after OLT. Interestingly, the only patient with changes in a major virus population after OLT had changes in the CCAAT-box of the S-promoter. As shown by gel shift analysis, this mutation was associated with loss of specific binding to this element and thus probably led to dysregulation of S-gene transcription. Major changes in the pre-S genome are mainly seen before OLT, and HBV reinfection does occur with the intact hepatocyte attachment sites after OLT. Anti-HBs (hepatitis B immune globulin [HBIg]) creates no selection pressure on the pre-S region. The mutation in the CCAAT-box of the S-promoter potentially leads to its dysregulation and may be associated with the occurrence of fibrosing cholestatic hepatitis after OLT.